Logan, who was a Tesco store assistant, admitted killing his brother during a police interview on January 13.

He told officers: “It was not my intent to kill him but I did do it.”

When charged with the attempted murder of Ms Williams, he said: “I thought she was out of the room.” He added: “I did not wish to murder my parents.”

In mitigation, defence QC Shelagh McCall said Logan had shown genuine remorse and views the murder of his brother as “horrific” and that it cannot be justified.

She told the court that the 27-year-old had attempted suicide in prison and is under high observation.

The judge accepted court reports that Logan has “abnormal personality traits” and features of autism but said there was no suggestion that Logan had a mental disorder and was fully criminally responsible for his actions.

Ms McCall also referred to a letter that Logan’s parents had written to the court which said they “find it extremely difficult to reconcile the Blair they know with the Blair who caused Cameron’s death”.

In passing sentence, Lady Scott said: “I cannot imagine the pain they will forever endure from what you did, losing in effect both of their sons.”